The invention relates to an x-ray diagnostic system comprising means for the fixed specification of the exposure time of an x-ray photograph, as well as comprising adjustment means for selecting the setting of the x-ray tube voltage and the mAs-product.
An x-ray diagnostic system of this type is described in the German AS No. 2,116,705. The exposure time is here specified by a planigraphic apparatus for preparation of x-ray laminograms and is determined by the selected movement path of the x-ray tube and of the image layer carrier. In the case of the known x-ray diagnostic system, the computer determines, from the specified exposure time and the adjusted mAs-product, the necessary x-ray tube current and effects its adjustment in the x-ray diagnostic generator. In the case of an x-ray generator wherein the adjustment of the x-ray tube voltage proceeds via the filament current of the x-ray tube and the voltage drop at the generator internal resistance, brought about thereby, one is however, not free, with fixedly specified values for x-ray tube voltage, mAs-product, and exposure time, with regard to selection of the x-ray tube current; on the contrary, one is restricted to the operating points specified by the voltage drop curves. In addition, an exact observance of the adjusted mAs-product is not guaranteed in the case of a generator which determines the x-ray tube current via a computer circuit from mAs-product and exposure time and fixedly adjusts said x-ray tube current prior to the photographic exposure, since fluctuations of the x-ray tube current arising during a photographic exposure cannot be taken into account.